This invention relates to a cut-resistant ply-twisted yarn and fabrics made from that yarn that are useful in protective garments, especially garments known as turnout gear which are useful for firefighters, but such fabrics and garments also have use in industrial applications where workers may be exposed to abrasive and mechanically harsh environments where fire and flame protection is needed. The garments, which include coats, coveralls, jackets, and/or pants can provide protection against fire, flame, and heat.
Most turnout gear commonly used by firefighters in the United States comprise three layers, each performing a distinct function. There is an outer shell fabric often made from flame resistant aramid fiber such as poly (meta-phenylene iosphthalamide) (MPD-I) or poly (para-phenylene terephthalamide) (PPD-T) or blends of those fibers with flame resistant fibers such as polybenzimidazoles (PBI). Adjacent to the outer shell fabric is a moisture barrier and common moisture barriers include a laminate of Crosstech® PTFE membrane on a woven MPD-I/PPD-T substrate, or a laminate of neoprene on a fibrous woven polyester/cotton substrate. Adjacent the moisture barrier is an insulating thermal liner which generally comprises a batt of heat resistant fiber.
The outer shell serves as initial flame protection while the thermal liner and moisture barrier protect against heat stress.
Since the outer shell provides primary defense it is desirable that this shell be durable and able to withstand abrasion and resist tearing or cutting in harsh environments. This invention provides for such a fabric that is preferably flame resistant and has good tear, cut, and abrasion attributes.
There are a number of fabrics described in the prior art which utilize bare steel wires and cords, primarily as armored fabrics. For example, WO 9727769 (Bourgois et al.) discloses a protective textile fabric comprising a plurality of steel cords twisted together. WO 200186046 (Vanassche et al.) discloses a fabric comprising steel elements used to provide cut resistance or reinforcement for protective textiles. The steel elements are either a single steel wire, a bundle of non-twisted steel wires, or a cord of twisted steel fibers. GB 2324100 (Soar) discloses a protective material made from twisted multi-strand cable which may be stitched to one or more layers of Kevlar® to form a unitary material. The use of large quantities of bare metal wire presents processing challenges and garment aesthetic (comfort and feel) problems and is undesirable.
U.S. Pat. No. 4,470,251 (Bettcher) discloses a cut resistant yarn made by winding a number of synthetic fibers yarns, such as nylon and aramid, around a core of strands of stainless steel wire and a high strength synthetic fiber such as aramid, and a safety garment made from the wound yarn.
U.S. Pat. No. 5,119,512 (Dunbar et al.) discloses a protective fabric made from cut resistant yarn comprising two dissimilar non-metallic fibers,.at least one being flexible and inherently cut resistant and the other having a level of hardness at above three Mohs on the hardness scale.
While inorganic filaments such as steel can provide useful cut resistance in fabrics, incorporating those inorganic filaments into fabrics is not a trivial problem, especially when combining those inorganic filaments with other continuous organic filament yarns. Most multifilament yarns containing continuous organic filaments have initial twist to maintain cohesion of the yarn. If an inorganic filament is simply twisted into the previously twisted yarns, the final yarn is too lively, that is it has too much twist and tends to twist and wrap onto itself and snag during weaving, preventing high quality fabrics from being produced. Further, if the inorganic filament is combined with the multifilament yarn without twist or with very low twist, the resulting yarn will not have adequate cohesion to be woven. What is needed is a method of providing a twisted yarn containing both multifilament yarns of continuous filaments and continuous inorganic filaments that has low liveliness and is easily woven into a fabric.